This code fails the assert:

> class x {}
>  int[x[]] foo;
>  int main() {
>   x[] key = new x[1];
>    foo[key] = 0;
>   assert(key in foo);
>    return 0;
> }

I went back and tested this snippet on 0.92, and it segfaults (every time I run it) rather than asserts.  However, on my larger program (where I first found this bug), it used to only segfault sometimes. Most of the time it used to work.